tbe

TBE is caused by the zoonotic tick-borne encephalitis virus (TBEV), a member of the genus Flavivirus within the Flaviviridae family [6]. It is classified as a single virus species with three subtypes: the European subtype, the Siberian subtype and the Far Eastern subtype together representing the geographic distribution of the virus.

Ixodes ricinus is the sole vector of the European subtype while I. persulcatus serves as vector for the two other subtypes. Dermacentor nuttalli, however, may share this role in southern Siberia and northern Mongolia (unpublished results).

TBE seems to have a minor public health impact in Denmark, France, Greece, Italy and Norway.

Biphasic course

1) First viraemic phase: fever, malaise, headache, myalgia, sometimes gastrointestinal symptoms, leukopenia, thrombocytopenia and elevated liver enzymes after an incubation period of one to two weeks. These non-specific symptoms last for about 2-4 days, often followed by a symptom-free interval of up to one week.

2) Second phase: occurs in approximately a quarter of the infected patients and shows the clinical signs of meningitis, meningoencephalitis, meningoencephalomyelitis or meningoencephaloradiculitis of different severity.

The three TBE virus subtypes differ with regard to disease severity but the tendency is become a chronic disease or to cause extremely prolonged infections in some patients.

European subtype

The less severe strain. Cause mild encephalitis.

Siberian subtype

Causes a serious disease (fatality rate between 1 and 3%).

Far Eastern subtype

The most severe form can cause severe febrile illness, frequently associated with encephalitis, and a fatality rate up to 35%.

Laboratorial

Haematology may show physiological leucocyte counts, but the differential blood count may indicate monocytosis and lymphopenia or leukopenia with physiological counts of both monocytes and lymphocytes.

Elevated total leucocyte and mononuclear cell counts as well as high protein concentration in the liquor are typical indicators for encephalitis and are commonly described in cases of clinical TBE in dogs

Specific diagnostic procedures

Detection of TBE virus in the serum during viremia by one of the many published RT-PCRs or real-time RT-PCRs.

Viral antigen can also be detected by immunohistopathology of brain tissues after necropsy